The present invention relates to a projector that enlarges and projects an image with a projection lens onto a projection screen, and more particularly, to a structure for coupling a ceiling suspension attachment to a projector.
A projector is used in a standing state, in which the projector is arranged on, for example, the surface of a table, or a suspended state, in which the projector is suspended from a ceiling.
When using the projector in a standing state, the projector is arranged so that the top surface of its outer case is located at an upper side, and the bottom surface of the outer case is located at a lower side. When the projector is used in the standing state, the top surface and bottom surface of the outer case are normally referred to as the upper surface and the lower surface. Further, the surface of the outer case in which a projection lens is arranged is normally referred to as a front surface. In this specification, a view of the projector taken in the standing state will be used as the frame of reference for the left, right, front, and rear directions.
When using the projector in a suspended state, the projector is arranged so that the top surface of the outer case is located at the lower side and the bottom surface of the outer case is located at the upper side. In this state, an attachment is coupled to the bottom surface of the outer case. The projector is suspended by the attachment from a ceiling. The present invention provides a structure for coupling the attachment to the bottom surface of the outer case.
Japanese Laid-Open Patent Publication No. 2008-197389 describes a prior art example of such a coupling structure, which is shown in FIG. 6.
Referring to FIG. 6(a), an attachment 101, which is used to suspend a projector from a ceiling, is coupled to a bottom surface 103 of the outer case 102. More specifically, referring to FIG. 6(b), a coupling screw 104 is inserted into a hole 105, which extends through the attachment 101, and directly fastened to a threaded hole 107 formed in a bottom wall 106, which defines the bottom surface 103 of the outer case 102. In this manner, the ceiling suspension attachment 101 is coupled to the bottom surface 103 of the case 102.
Japanese Laid-Open Patent Publication No. 2000-122180 describes another example of a coupling structure, which is shown in FIG. 7.
In the same manner as the prior art example described above, a ceiling suspension attachment 201 is coupled to a bottom surface 203 of an outer case 202 of a projector. More specifically, as shown in FIG. 7, a coupling screw 204 is inserted into a hole 205, which extends through the attachment 201, and fastened to a nut 207, which is arranged in a bottom wall 206, which defines the bottom surface 203 of the outer case 202. The nut 207 is fitted to a sleeve 208, which is formed on the bottom wall 206. The nut 207 prevents separation of the coupling screw 204 from the sleeve 208 in the axial direction. A cap 209 covers the sleeve 208 at the inner side of the bottom wall 206. The cap 209 is fixed to projections 210 extending from the inner surface of the bottom wall 206. In this manner, the ceiling suspension attachment 201 is coupled to the bottom surface 203 of the outer case 202.
In Japanese Laid-Open Patent Publication No. 2008-197389, the coupling screw 104, which is for coupling the attachment 101 to the bottom surface 103, is directly fastened to the threaded hole 107, which is formed in the bottom wall 106 of the outer case 102. The threaded hole 107 has low strength, and the coupling screw 104 can easily loosen from the bottom wall 106.
In Japanese Laid-Open Patent Publication No. 2000-122180, the coupling screw 204 is fastened to the nut 207, which is fitted to the bottom wall 206. Thus, the strength of the coupled portion is sufficient. However, the weight of the projector or a force applied to the projector acts greatly on the joint between the nut 207 and the bottom wall 206. Thus, when used over a long period of time, wear or partial breakage of the bottom wall 206 may occur and lower the coupling strength of the nut 207.